Aircraft may collide with birds while in flight. In some instances, birds may collide with a gas turbine engine. In gas turbine engines having a fan, the fan blades may absorb the brunt of an impact. The impulse from impact may result in temporarily elevated strain in the fan blades. The area subjected to the increased strain may be the transition zone on the leading edge of the fan blade below the sheath. Stiff fan blades, for example, may be susceptible to damage at such area during an impact event.